Medical applications of biopolymeric membranes are manifold. See, e.g., Shu-Tung Li, Biologic Biomaterials: Tissue-Derived Biomaterials (Collagen). In: Biomedical Engineering Handbook, Ed. J. D. Bronzino, 627-647, CRC Press, Inc. Boca Raton, Fla., 2000.
Biopolymeric membranes, such as collagen membranes, can be made by air-drying a biopolymeric fibers-containing solution, or applying an acid or a base solution of dispersed biopolymeric fibers on a flat surface. Li disclosed in U.S. Pat. No. 5,206,028 a method of preparing a collagen membrane by first freeze-drying a collagen dispersion to form a sponge, which is then humidified, compressed, and subjected to chemical crosslinking. Chu et al., on the other hand, disclosed in U.S. Pat. No. 4,725,671 a method of preparing a gel from an atelocollagen solution and then compressing and air-drying the gel to form a collagen membrane.
The biopolymeric fibers in sheet membranes prepared by the prior art methods are randomly oriented. Such membranes generally have low mechanical strength and are only useful in applications where mechanical strength of the device is not a critical factor for function. They are not suturable and tend to tear with a slight suture tug. As most soft tissue enforcement materials require extensive mechanical strength so that they can be easily secured in place either by using sutures, staples, tags, or screws, mechanical strength becomes a critical factor in designing biopolymeric fiber-based membranes for applications in soft tissue repair.